1. Field of the Invention
The present invention relates to a method of producing electrical connection members for use in forming electrical connections between electrical circuit parts.
2. Description of the Related Background Art
It is common practice to connect electrical circuit parts by a wire-bonding method, a CCB (controlled collapse bonding) method, a TAB (tape automated bonding) method, a method utilizing anisotropic conducting film, a method utilizing a sheet-like electrical connection member of the type in which pins made of electrically conductive material are buried in electrical insulation resin, or the like.
Of these methods, the method utilizing a sheet-like electrical connection member of the type in which pins made of electrically conductive material are buried in electrical insulation resin has a number of advantages. For example, electrical circuit parts can be connected under constant pressure so that a stable connection therebetween can be achieved. Variations in connection resistance can be kept to a minimum and it is possible to increase the density of the connecting portions of the electrical connection member.
As shown in FIGS. 1(a) and 1(b), the above-described type of electrical connection member 125 has a construction in which pins 121 made of electrically conductive material are buried in a sheet-like carrier made of electrical insulation resin 123. The illustrated electrical connection member 125 has heretofore been produced by the method shown in FIG. 2 (disclosed in, for example, U.S. Pat. No. 3,862,790).
This method of producing the above-described type of electrical connection member comprises the steps of lacing, as shown in FIG. 2, a conductor wire 124 around rods 122 which are disposed at a desired pitch in a staggered manner, the conductor wire 124 having a predetermined diameter and to be cut into the pins 121 which constitute part of each electrical connection member 125; molding this conductor wire 124 with the resin 123 having electrical insulation properties; curing the resin 123; and cutting the cured product into the sheet-like electrical connection members 125 each having a desired thickness.
However, the above-described conventional method of producing electrical connection members has a number of problems. First, since it takes a long time to cure the resin having electrical insulation properties, the production of electrical connection members involves a timeconsuming operation. Second, since the cured product is cut into sheet-like electrical connection members, it is difficult to minimize the sheet thickness and only relatively thick electrical connection members can be obtained. Third, if an inappropriate cutting method is selected, conductor wire which is buried at high density may be deformed or damaged during cutting. In a case where an electrical connection member including a deformed portion of the conductor wire is used in practice, an unwanted conducting path may be formed due to the contact between adjacent deformed portions of the conductor wire which constitutes electrically conducting portions of the electrical connection member. Fourth, since the electrically conducting portions are formed by utilizing the method of lacing conductor wire in a staggered manner, the density of the electrically conducting portions is limited. Another disadvantage of the electrical connection member produced by the aforesaid method is that, since the conductor wire which constitutes the electrically conducting portions is approximately equal in diameter to holes which retain the conductor wire in the resin layer of the electrical connection member, the conductor wire tends to easily come away from the resin layer. This disadvantage may lead to a deterioration in the reliability of electrical connection. A further disadvantage of the electrical connection member produced by the aforesaid method is that, since the surfaces of the sheet-like carrier made of the resin having electrical insulating properties are flush with the contact ends of the electrically conducting portions, it is difficult to achieve a reliable connection with electrical circuit parts. To solve this problem, it is preferable that the contact ends of the electrically conducting portions be formed into a bump-like configuration. However, to attain the bump-like configuration, it is necessary that the surface of the resin carrier of the sheet-like electrical connection member be etched to expose electrically conductive members made from the conductor wire and the exposed conductive members be then melted either mechanically or thermally. Accordingly, the production process inevitably becomes complicated.